Systems and Methods of Non-Invasive Continuous Adaptive Tuning of Digitally Controlled Switched Mode Power Supply Based on Measured Dynamic Response

ABSTRACT

Example embodiments of the systems and methods of non-invasive continuous adaptive tuning of digitally controlled switched mode power supply based on measured dynamic response disclosed herein rely on time domain measurements for the tuning rather than on frequency response to automatically tune the system for stability and good dynamic performance. In particular, an algorithm directly measures overshoot and settling time to transients. Using this information, the algorithm minimizes both overshoot/undershoot and settling time by adjusting the parameters of a digital compensator. Since time domain measurements are directly used, the implementation does not require an additional perturbation in the system that otherwise would be necessary.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This continuation application claims priority to U.S. patent applicationSer. No. 14/947,495, filed Nov. 20, 2015, which application isincorporated herein by reference.

TECHNICAL FIELD

The present disclosure is generally related to electronics and, moreparticularly, is related to power management.

BACKGROUND

A switched mode power supply (power converter, SMPS) as provided in FIG.1 is an electronic power supply that incorporates switching regulator110 to convert electrical power efficiently. Like other power supplies,an SMPS transfers power from source 120, for example, mains power, toload 130, such as a personal computer, while converting voltage andcurrent characteristics. Unlike a linear power supply, pass transistor140 of a switched mode power supply continually switches betweenlow-dissipation, full-on and full-off states, and spends very littletime in the high dissipation transitions, which minimizes wasted energy.Ideally, a switched mode power supply dissipates no power. Voltageregulation is achieved by varying the ratio of on-to-off time. Incontrast, a linear power supply regulates the output voltage bycontinually dissipating power in the pass transistor. This higher powerconversion efficiency is an important advantage of a switched mode powersupply.

Switching regulators may be used as replacements for linear regulatorswhen higher efficiency, smaller size or lighter weight are required.They are, however, more complicated; switching currents can causeelectrical noise problems if not carefully suppressed, and simpledesigns may have a poor power factor.

In an SMPS, the output current flow depends on the input power signal,the storage elements and circuit topologies used, and also on thepattern used (e.g., pulse-width modulation with an adjustable dutycycle) to drive the switching elements. The spectral density of theseswitching waveforms has energy concentrated at relatively highfrequencies. As such, switching transients and ripple introduced ontothe output waveforms may be filtered.

Although a switching power supply may offer greater efficiency,disadvantages include greater complexity, the generation ofhigh-amplitude, high-frequency energy that the low-pass filter mustblock to avoid electromagnetic interference (EMI), a ripple voltage atthe switching frequency and the harmonic frequencies thereof.

A power converter's transient performance is subject to uncertaintiesand non-idealities in the components and controller. Thesenon-idealities can deteriorate response to dynamic changes in the systemand/or cause the system to approach instability. Prior art solutions tothis problem have included automatic one-time or continuous adjustmentof the control parameters based on frequency response techniques. Thereare heretofore unaddressed needs with these previous solutions.

SUMMARY

Example embodiments of the present disclosure provide systems ofnon-invasive continuous adaptive tuning of digitally controlled switchedmode power supply based on measured dynamic response. Briefly described,in architecture, one example embodiment of the system, among others, canbe implemented as follows: a switch mode power supply (SMPS) controller;and an adjustable compensator configured to receive time domaininformation based on a measured transient of an output voltage of anSMPS controlled by the SMPS controller and to send a compensation signalto the SMPS controller to compensate for the transient on the outputvoltage.

Embodiments of the present disclosure can also be viewed as providingmethods for non-invasive continuous adaptive tuning of digitallycontrolled switched mode power supply based on measured dynamicresponse. In this regard, one embodiment of such a method, among others,can be broadly summarized by the following steps: providing an outputvoltage with a switch mode power supply (SMPS), the SMPS comprising anSMPS controller; receiving information related to time domain transientson the output voltage; and sending an adjustable compensation signal tothe SMPS controller to adjust for the transients on the output voltage.

Embodiments of the present disclosure can also be viewed as providingcircuits for non-invasive continuous adaptive tuning of digitallycontrolled switched mode power supply based on measured dynamicresponse. In this regard, one embodiment of such a method, among others,can be broadly summarized by the following elements: a switch mode powersupply (SMPS) circuit configured to provide a regulated output voltage,the SMPS circuit comprising: a controller configured to control theregulation of the output voltage, the controller comprising anadjustable compensator configured to receive information based on a timedomain transient on the regulated output voltage and to adjust a pulsewidth modulation signal used to regulate the output voltage based on thereceived information on the time domain transient

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram of a switched mode power supply (SMPS).

FIG. 2 is a circuit diagram of an SMPS with one-time, startup tuning.

FIG. 3 is a circuit diagram of an SMPS with continuous tuning based onan external perturbation signal.

FIG. 4 is a circuit diagram of an example embodiment of a system ofnon-invasive continuous adaptive tuning of digitally controlled switchedmode power supply.

FIG. 5 provides signal diagrams for tuning example embodiments of thesystem of FIG. 4.

FIG. 6 is a signal diagram comparing the results of tuning with a fixedcompensator and with example embodiments of the system of FIG. 4.

FIG. 7 is a signal diagram comparing the results of tuning with a fixedcompensator and with example embodiments of the system of FIG. 4.

FIG. 8 is a flow diagram of an example embodiment of a methodnon-invasive continuous adaptive tuning of digitally controlled switchedmode power supply.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described more fullyhereinafter with reference to the accompanying drawings in which likenumerals represent like elements throughout the several figures, and inwhich example embodiments are shown. Embodiments of the claims may,however, be embodied in many different forms and should not be construedas limited to the embodiments set forth herein. The examples set forthherein are non-limiting examples and are merely examples among otherpossible examples.

Example embodiments of the systems and methods of non-invasivecontinuous adaptive tuning of digitally controlled switched mode powersupply based on measured dynamic response disclosed herein rely on timedomain measurements for the tuning rather than on frequency response toautomatically tune the system for stability and good dynamicperformance. In particular, an algorithm directly measures overshoot andsettling time to transients. Using this information, the algorithmminimizes both overshoot/undershoot and settling time by adjusting theparameters of a digital compensator. Since time domain measurements aredirectly used, the implementation does not require an additionalperturbation in the system that otherwise would be necessary as inprevious solutions.

In particular, example embodiments of the systems and methods disclosedherein rely on transients already present in the system (that is, load,line, or reference transients). Using transients already present in thesystem presents the ability to tune based on parameters that affect endequipment performance (time domain response) while not requiring anyadditional signal injections into the system. Example embodimentsdisclosed herein do not require any perturbation in the system otherthan those that are already present (load, line, and referencetransients as non-limiting examples). Previous solutions have relied ontuning the frequency domain response of the power supply, which hasnon-ideal translation to time domain responses.

In designing a switching power supply, the selected values of inductanceand capacitance may vary greatly. One designer may select a capacitor atone microfarad and another may select one milli-farad. Additionally, theinductance choice may vary greatly from design to design. Even if anappropriate inductance value is selected, the tolerance of that valuemay vary by plus or minus 20-30%; similar issues apply to thecapacitance and even to the capacitor equivalent series resistance(ESR). Additionally, even if all of the initial parameter values areknown, the capacitor values may vary as much as 30% over time withcapacitor ESR varying as much as 200% due to aging of components in thefield. If all of these factors are combined, the implications are that,in regards to the dynamics of the converter, the ability to regulate theoutput voltage with changes in input voltage and load current issignificantly degraded. Additionally, due to a potentially wide inputoperating range, the control loop is often conservatively designed suchthat stability may be maintained. A conservative design compensates forthe wide variations of inductance, capacitance and capacitor ESR overtime.

Previous mitigation techniques include circuits of FIG. 2 and FIG. 3. Inthe circuit of FIG. 2, the feedback loop is designed to be slow toproduce a fixed feedback loop compensation network. The slow responseenables handling of wide parameter variations. Controller 210 provides asingle tuning instance on startup. Since it only tunes the system uponstartup, it cannot account for variations over time and the processingcan be complicated. It also has an inherent disadvantage of requiringadditional capacitance to remain within the output band overloadtransients.

In another previous solution with auto-tuning in which, upon startup,the parameters of the control loop are tuned by compensating based onthe reaction of some measured parameters in the system to a signalinjected into the converter on startup. In this solution, someattributes about the system are measured to induce some informationabout the inductance and capacitance parameters of the converter onstartup. Signal processing techniques are used to select a compensatorvalue that would be appropriate for the measured values on startup.Disadvantages of this technique include operation only on startup orduring periodic intervals. Without continual compensation, parametervariations over time are not effectively managed. Another disadvantageto this technique is the use of an injected signal that is not normallyin the system. This injected signal may cause additional output voltageripple and requires additional complicated processing.

The circuit of FIG. 3 provides another previous solution, which involvescontinuous tuning during operation of the converter. The continuoustuning has some similar results. It measures values of the system andcontinually adjusts the parameters of the control loop in reaction tothose measured values. This solution solves some of the problems withrespect to component variations due to aging, to parameter uncertaintyupon startup, and to component selection. However, it has similardrawbacks as it requires an external perturbation. A signal, such assquare wave 310, is injected into the feedback loop. That perturbationsignal is used to tune the system, while resulting in some undesiredripple on the output. It also requires some additional complicatedprocessing.

As provided in FIG. 4, an example embodiment of the systems and methodsof non-invasive continuous adaptive tuning of digitally controlledswitched mode power supply based on measured dynamic response disclosedherein implements a control loop (digital or analog) that measuresoutput voltage 408 of SMPS 405 and adjustable compensator 430 to adjustthe parameters of the feedback loop. When an output load transientoccurs, for example, output voltage 408 exhibits an overshoot or anundershoot, a natural measureable transient of the system. Outputvoltage 408 may be converted by analog to digital converter 410 formeasurement of the transient information by settling time detector 415and overshoot detector 420 (measures overshoot and undershoot). Thetransients and the response to those transients are used to tune theload step response. Instead of injecting a signal and using somecomplicated processing, example embodiments use the transientinformation to tune the transient response. When a load step occurs, theovershoot or undershoot and the settling time are measured based on thenatural load transient.

In example embodiments, compensator adjustment algorithm module 440adjusts the parameters of adjustable compensator 430 in a way thatoptimizes it for the next load transient. As more load transients occur,the controller becomes more optimized. After a certain number oftransients occur, the algorithm produces an approximation of an optimumload step response. No external perturbation is used and the processingis simple.

In example embodiments, the system uses a number of iterations which mayresult in a delay in approaching an optimum load step. At startup, thevery first transient response may not be ideal. To compensate for thisdelay, optional startup tuning algorithm module 480 may inject anatypical startup tuning signal that induces a small step response. Thisstep response is measured and induces parameters that may be used forstartup. The startup tuning signal parameters may be provided by ω₀detector 460 and Q factor detector 470. Q factor detector 470 and ω₀detector 460 detect the open loop converter frequency response. If asmall step is injected in the duty cycle, the output will ring. Theringing depends on the Q and the ω₀ of the power converter. Adjustmentsignals are sent from startup tuning algorithm module 480 and adjustablecompensator 430 to multiplexer 490, which sends a final adjustmentsignal to pulse width modulator 495 for regulating the output of SMPS405. A first signal from startup tuning algorithm module 480 tomultiplexer 490 is the output of startup tuning algorithm module 480. Asecond signal from startup tuning algorithm module 480 to multiplexer490 indicates to multiplexer 490 when the startup tuning process iscompleted and switches the mux inputs. After startup, compensatoradjustment algorithm module 440 uses the measurements from settling timedetector 415 and overshoot detector 420 to fine-tune the response.

FIG. 5 provides signal diagrams of the effects on overshot and settlingtime due to changes in gain and zero of the loop response. In signaldiagram 510, gain K is increased until the optimum overshoot is reached.Signal diagram 520 demonstrates that a change in the zero location ofthe response loop has a small effect on the overshoot. In signal diagram530, gain K is increased until the optimum settling time is reached. Insignal diagram 510, the zero location of the response loop is decreaseduntil the optimum settling time is reached. In adjusting the response tothe transients, increasing the gain or decreasing the location of thezero in the response loop will decrease the overshoot while increasingthe bandwidth of the response. At some point while increasing the gain,a minimum overshoot may be reached. If the gain is increased beyond thatpoint, the phase margin of the loop response is decreased, which resultsin increasing the overshoot. The minimum overshoot tracking algorithmdetermines the point at which increasing the gain results in a minimumovershoot. A similar algorithm is used for the settling time. Althoughboth the overshoot and the settling time are a function of the gain,only the settling time is affected by adjusting the zero point of theresponse loop.

The overshoot or undershoot is measured (or the settling time),optionally starting at a point based on the startup tuning algorithm.Then, the gain is increased and the zero location is decreased. When thenext transient occurs, if the overshoot and settling time of this nexttransient is improved then the adjustment is proceeding correctly. Thisprocess may be performed iteratively until the minimumovershoot/undershoot (or settling time) is reached as previouslydiscussed. The time it takes to reach the minimum overshoot (or settlingtime) may depend on the size of the steps in the adjustment algorithm.If the gain increase is relatively large, approaching the minimumovershoot may occur relatively quickly; however, referring back tosignal diagram 510, the overshoot may also oscillate between a point onthe very far left on the overshoot curve and a point on the very farright of the overshoot curve. The step size may be chosen such that itis as large as possible, while still able to approach the minimum point.

FIG. 6 provides a signal diagram of a comparison of the transientsbetween using a fixed compensator, shown on the left, and using theexample embodiments of the system disclosed herein, shown on the right,when a 1.65 A load step occurs on the output. Example embodiments of thesystem disclosed herein provide a reduction of fifty percent of theovershoot over using the fixed compensator on the left. Exampleembodiments of the system disclosed herein also result in over an eightypercent reduction in settling time.

FIG. 7 provides a signal diagram of a comparison of the transientsbetween using a fixed compensator, shown on the left, and using theexample embodiments of the system disclosed herein, shown on the right,when a 2.5 A load step occurs on the output. Example embodiments of thesystem disclosed herein provide a reduction of fifty percent of theundershoot over using the fixed compensator on the left. Exampleembodiments of the system disclosed herein also result in a ninety-fourpercent reduction in settling time.

FIG. 8 provides a flow diagram of an example embodiment of a method ofnon-invasive continuous adaptive tuning of digitally controlled switchedmode power supply based on measured dynamic response. In block 810, anoutput voltage is provided with a switch mode power supply (SMPS), theSMPS comprising an SMPS controller. In block 820, information related totime domain transients on the output voltage is received. In block 830,an adjustable compensation signal is sent to the SMPS controller toadjust for the transients on the output voltage.

Example embodiments of the systems and methods of non-invasivecontinuous adaptive tuning of digitally controlled switched mode powersupply based on measured dynamic response disclosed herein uses a simplealgorithm which accounts for parameter variations on startup and overtime. Example embodiments are easy to implement and are hardwareefficient. No external perturbation is introduced to the system. Thecompensator adjustment algorithm tunes the response based on a keyperformance parameter, such as the dynamic performance, whereas otheralgorithms tune based on parameters such as phase margin and crossoverfrequency, for example. Phase margin and crossover frequency arefrequency response based considerations. Although phase margin andcrossover frequency have a correlation to time domain measurements ofovershoot and settling time, the actual overshoot and settling time arekey performance parameters. Example embodiments disclosed herein adjustbased directly on those key performance parameters.

The flow chart of FIG. 8 shows the architecture, functionality, andoperation of a possible implementation of the software for non-invasivecontinuous adaptive tuning of digitally controlled switched mode powersupply based on measured dynamic response. In this regard, each blockrepresents a module, segment, or portion of code, which comprises one ormore executable instructions for implementing the specified logicalfunction(s). It should also be noted that in some alternativeimplementations, the functions noted in the blocks may occur out of theorder noted in FIG. 8. For example, two blocks shown in succession inFIG. 8 may in fact be executed substantially concurrently or the blocksmay sometimes be executed in the reverse order, depending upon thefunctionality involved. Any process descriptions or blocks in flowcharts should be understood as representing modules, segments, orportions of code which include one or more executable instructions forimplementing specific logical functions or steps in the process, andalternate implementations are included within the scope of the exampleembodiments in which functions may be executed out of order from thatshown or discussed, including substantially concurrently or in reverseorder, depending on the functionality involved. In addition, the processdescriptions or blocks in flow charts should be understood asrepresenting decisions made by a hardware structure such as a statemachine.

The logic of the example embodiment(s) can be implemented in hardware,software, firmware, or a combination thereof. In example embodiments,the logic is implemented in software or firmware that is stored in amemory and that is executed by a suitable instruction execution system.If implemented in hardware, as in an alternative embodiment, the logiccan be implemented with any or a combination of the followingtechnologies, which are all well known in the art: a discrete logiccircuit(s) having logic gates for implementing logic functions upon datasignals, an application specific integrated circuit (ASIC) havingappropriate combinational logic gates, a programmable gate array(s)(PGA), a field programmable gate array (FPGA), etc. In addition, thescope of the present disclosure includes embodying the functionality ofthe example embodiments disclosed herein in logic embodied in hardwareor software-configured media.

Software embodiments, which comprise an ordered listing of executableinstructions for implementing logical functions, can be embodied in anycomputer-readable medium for use by or in connection with an instructionexecution system, apparatus, or device, such as a computer-based system,processor-containing system, or other system that can fetch theinstructions from the instruction execution system, apparatus, or deviceand execute the instructions. In the context of this document, a“computer-readable medium” can be any means that can contain, store, orcommunicate the program for use by or in connection with the instructionexecution system, apparatus, or device. The computer readable medium canbe, for example but not limited to, an electronic, magnetic, optical,electromagnetic, infrared, or semiconductor system, apparatus, ordevice. More specific examples (a nonexhaustive list) of thecomputer-readable medium would include the following: a portablecomputer diskette (magnetic), a random access memory (RAM) (electronic),a read-only memory (ROM) (electronic), an erasable programmableread-only memory (EPROM or Flash memory) (electronic), and a portablecompact disc read-only memory (CDROM) (optical). In addition, the scopeof the present disclosure includes embodying the functionality of theexample embodiments of the present disclosure in logic embodied inhardware or software-configured media.

Although the present disclosure has been described in detail, it shouldbe understood that various changes, substitutions and alterations can bemade thereto without departing from the spirit and scope of thedisclosure as defined by the appended claims.

Therefore, at least the following is claimed:
 1. A system comprising: aswitch mode power supply (SMPS) controller; and an adjustablecompensator configured to continuously receive time domain informationbased on a measured transient of an output voltage of an SMPS controlledby the SMPS controller and to continuously send a compensation signal tothe SMPS controller to compensate for the transient on the outputvoltage.
 2. The system of claim 1, wherein the measured transientcomprises at least one of overshoot/undershoot and output voltagesettling time.
 3. The system of claim 1, wherein the measured transientinformation is provided by an analog to digital converter.
 4. The systemof claim 1, wherein the compensation signal is adjusted according to acompensation adjustment algorithm.
 5. The system of claim 1, wherein thecompensation signal is provided without using an external perturbationsignal.
 6. A method comprising: providing an output voltage with aswitch mode power supply (SMPS), the SMPS comprising an SMPS controller;continuously receiving information related to time domain transients onthe output voltage; and sending an adjustable compensation signal to theSMPS controller to continuously adjust for the transients on the outputvoltage.
 7. The method of claim 6, wherein the measured transientcomprises at least one of overshoot/undershoot and output voltagesettling time.
 8. The method of claim 6, wherein the measured transientinformation is provided by an analog to digital converter.
 9. The methodof claim 6, further comprising adjusting the adjustable compensationsignal according to a compensation adjustment algorithm.
 10. The methodof claim 6, further comprising providing the adjustable compensationsignal without using an external perturbation.
 11. A circuit comprising:a switch mode power supply (SMPS) circuit configured to provide aregulated output voltage, the SMPS circuit comprising: a controllerconfigured to control the regulation of the output voltage, thecontroller comprising an adjustable compensator configured tocontinuously receive information based on a time domain transient on theregulated output voltage and to continuously adjust a pulse widthmodulation signal used to regulate the output voltage based on thereceived information on the time domain transient.
 12. The circuit ofclaim 11, wherein the time domain transient comprises at least one ofovershoot/undershoot and output voltage settling time.
 13. The circuitof claim 11, wherein the information on the time domain transient isprovided by an analog to digital converter.
 14. The circuit of claim 11,wherein the pulse width modulation signal is adjusted without using anexternal perturbation signal.